The present invention relates to a bonded layer protection structure for a wear resistant component. More specifically, the invention relates to a bonded layer protection structure, which can be put to sufficient practical use in place of conventional solder bonding by increasing resistances to water and chemicals of a portion bonded by an adhesive between a cutting portion as a wear resistant member and a base metal as a main body portion in a wear resistant component such as a cutting tool.
For example as shown in FIG. 11, a knife-shaped cutting blade 10 used for a bookbinder or a paper machine tool is constructed by bonding a cutting portion 12 made of high-speed tool steel or the like to a base metal 14 made of common steel. In addition, a slide rail 16 for supporting a structure to be freely slid shown in FIG. 12, and a work rest 18 for supporting various works used for, for example a centerless grinding machine shown in FIG. 13 both have structures, where highly wear resistant blades 20 made of sintered hard alloys or the like are bonded to rail-shaped members 22. Generally, the cutting portion 12 and the blade 20 (referred to as xe2x80x9cwear resistance member 24xe2x80x9d, hereinafter), and the base metal 14 and the rail-shaped member 22 (referred to as xe2x80x9cmain body portion 26xe2x80x9d, hereinafter) are soldered together by using silver solder, copper solder or the like. The above-described cutting blade 10, the slide rail 26 and the work rest 18 are cutting tools or the like having high resistances to wear, which are constructed by bonding the wear resistant member 24 to the main body portion 26 of the base metal or the like, and these are generically referred to as xe2x80x9cwear resistant component 28xe2x80x9d hereinafter.
The wear resistant component 28 such as a cutting tool or the like constructed by bonding the wear resistant member 24 such as the cutting portion to the main body portion 26 such as the base metal is heated to about 800xc2x0 C. in soldering even when low-temperature silver solder is used. However, since the wear resistant member 24 as a material to be bonded and the main body portion 26 have intrinsic coefficients of thermal expansion, which are different from each other, heat distortion in an entire portion by the heating, cracks in the wear resistant member 24 and other problems inevitably occur. Thus, in the wear resistant component 28, when the wear resistant member 24 is soldered to the main body portion 26, it is necessary to suppress the occurrence of heat distortion as much as possible, and execute careful temperature control to prevent cracks. Accordingly, a worker needs long-time experience and skills.
Therefore, as shown in FIG. 14, for example, regarding the cutting tool 28 as the wear resistant component, an attempt has been made to bond the cutting portion 24 to the base metal 26 by an adhesive 30 and to put to practical use. In the case of this bonding by the adhesive, different from the case of the above-described soldering, heating exceeding 200xc2x0 C. is not carried out, and the work is basically carried out in a range of a normal temperature to 200xc2x0 C. or lower. Thus, no problems such as the above-described heat distortion or cracks occur. However, compared with the soldering, adhesive strength between the cutting portion 24 and the base metal 26 was not sufficient, this bonding by the adhesive has not yet been put to wide practical use. With recent improvements in adhesive, however, by selecting a type of adhesive, and securing a relatively large bonding area between the cutting portion 24 and the base metal 26, it is now possible to bond the cutting portion 24 to the base metal 26 with sufficient strength.
However, even for the cutting tool 28 constructed by bonding the cutting portion 24 to the base metal 26 by the adhesive 30, when the cutting portion 24 is worn with time because of use, the cutting portion 24 is removed from the cutting machine or the like each time, and subjected to repeated grinding. In this event, since a layer of the adhesive 30 is partially exposed in the bonded portion between the cutting portion 24 and the base metal 26, the exposed portion of the adhesive 30 is eroded by a grinding solution used for grinding, and deterioration gradually progresses. That is, even in the case of the adhesive for strongly bonding metal materials, resistances to water and chemicals have not yet been satisfactory. Thus, in the bonded portion between the cutting portion 24 and the base metal 26, where the adhesive 30 low in water and chemical resistances is exposed, as a result of being exposed to the grinding solution in grinding, peripheral adhesive strength is inevitably lowered. The adhesive has low reliability in terms of durability for long-time use, and thus the adhesive has not been put to practical use for bonding in the wear resistant component 28 such as the cutting tool having the wear resistant member 24 such as a cutting portion bonded to the main body portion 26 of the base metal or the like.
In addition, as described above, even if both members 24 and 26 can be bonded together by the adhesive 30 with strength necessary for the cutting tool 28 by securing a large bonding area between the cutting portion 24 and the base metal 26, compared with the above-described soldering, the bonding strength is usually lower. Consequently, when the cutting portion 24 is worn by repeated grinding, it is extremely dangerous to replace a cutter by another with a wear situation about equal to that during the conventional soldering set as a reference. When the cutting portion 24 is bonded to the base metal 26 by the adhesive 30, a large bonding area must be secured therefore. However, since the wear of the cutting portion 24 is always accompanied by wearing-out of the bonded portion, bonding strength of the adhesive is correspondingly lowered. Thus, in the case of the cutting tool 28 bonding the cutting portion 24 to the base metal 26 by the adhesive 30, a target of one type or another must be provided to clearly show a limit of use with consideration given to safety of a certain level. However, no presentations have been made yet to realize such.
The present invention was made to suitably solve the foregoing problems inherent in the wear resistant component such as a cutting tool constructed by bonding the wear resistant member such as s cutting portion to the main body portion such as a base metal. An object of the invention is to provide a protection structure for a bonded layer, which can be put to sufficient practical use in place of conventional soldering by increasing resistances to water and chemicals of an exposed portion of adhesive in the bonded layer. Another object of the invention is to provide means for clearly showing a limit of use with time of a wear resistant member effectively in a wear resistant component such as a cutting tool constructed by bonding a wear resistant member such as a cutting portion to a main body such as a base metal by adhesive.
In order to solve the above-described problem, and achieve the original object, in accordance with an aspect of the present invention, there is provided a bonded layer protection structure of a wear resistant component, comprising: a wear resistant component such as a cutting tool constructed by banding a wear resistant member such as a cutting portion to a main body portion such as a base metal by an adhesive. In this vase, a necessity part of an adhesive layer exposed portion in a bonded portion between the wear resistant member and the main body portion is covered with a filler or a covering material. For the filler, an adhesive having a resistance to water and/or a resistance to chemicals, or a silicon-containing caulking material is suitably used. For the covering material, a coating material having a resistance to water and/or a resistance to chemicals, a coating film of metal foil or a fluorocarbon resin, or a film by plating is suitably used.
In order to solve the above-described problem, and achieve the original object, in accordance with another aspect of the invention, there is provided a bonded layer protection structure of a wear resistant component, comprising: a wear resistant component such as a cutting tool constructed by bonding a wear resistant member such as a cutting portion to a main body portion such as a base metal by an adhesive. In this case, a necessary part of an adhesive layer exposed portion in a bonded portion between the wear resistance member and the main body portion is covered with a sticking member. For the sticking member, a plate-like, bar-like or piece-like metal member having a resistance to water and/or a resistance to chemicals is suitably used, and the sticking member is stuck to the adhesive layer exposed portion by adhesion or burying.
In order to solve the above-described problem, and achieve the original object, in accordance with yet another aspect of the invention, in the bonded layer protection structure of a wear resistant component, a marking indicating a limit of use is provided on at least one surface of the wear resistant member, before sufficient bonding strength cannot be secured because of a reduction in a bonding area of adhesive caused by frequent use or sharpen repairing, or the wear resistant member becomes thin to be broken off. The filler, the covering material or the sticking member itself may serve as such a marking indicating a limit of use of the wear resistant component.